The present invention is directed to a wire dot print head, and, in particular, to a wire dot print head having a driving coil for causing a print wire to impact on a platen.
Wire dot print heads are known in the art and fundamentally include a frame. A plurality of print wires mounted on respective levels are positioned within the frame. Drive coils are provided for driving each print wire. To print a pattern, the conventional wire dot print head requires 24 or 48 individual drive coils, levers and print wires to be positioned within the frame. Accordingly, one design problem of the conventional wire dot printer is to balance integration density with ease of assembly.
One such construction for overcoming the above concern is shown in U.S. Pat. No. 4,767,227 which describes a wire dot print head which provides for attaching a dot forming print wire at one end of a lever. The lever which is attracted by a drive coil is then mounted about a rotation shaft. A recess is formed within a yoke for fixing the rotation shaft thereto.
The prior art wire dot print head has proven satisfactory. However, the construction suffers from the inherent problem that the yoke requires a space in which to receive and position the rotating shaft provided on the lever. Hence, the number of units such as the lever which can be positioned in a single plane is limited and therefore integration density cannot be improved. Additionally, because the lever is mounted about a rotating shaft, the number of manufacturing processes increases making the assemblage more complicated resulting in increased cost. Additionally, in the prior art, to increase the number of wires to enhance print quality, it becomes necessary to stack the frame in multi-stage print wire layers. As a result, the overall size of the wire dot print head increases and because there is difference in length between individual print wires in each layer, the wire flex at the time of impact varies giving rise to a difference in print density.
Accordingly, it is desired to provide a wire dot print head in which integration density is increased while maintaining a structure which is easily manufactured.